1. Field of the Invention
The present invention relates generally to an arc welding process, and more particularly to an arc welding process having a welding arc generated between a consumable electrode and the materials to be welded and a welding torch is oscillated along the welding joint line, wherein the arc length is longer when the welding torch is located at the forward side of the oscillation than when the welding torch is located at the backward side of the oscillation with respect to the weld advancing direction.
2. Description of the Prior Art
Various welding processes wherein a consumable electrode is oscillated across the welding line to weld a butt joint or fillet joint have been proposed as, for example in U.S. Pat. No. 3,742,184 to Kobe Steel, Ltd. and U.S. Pat. No. 3,832,522 to Kobe Steel, Ltd. However, these processes cannot be applied to the narrow gap I groove butt welding of thick plates.
U.S. Pat. No. 2,280,770 to General Electric Company proposed a welding machine capable of oscillating back and forth a welding torch along a weld joint line for use in tack welding. Further, U.S. Pat. No. 3,818,176 to The Welding Institute proposes a welding process wherein the porosity of weld is reduced by a stirring action in the weld pool caused by an oscillation of the welding torch across and/or along the weld joint line.
Nevertheless, even with the above mentioned conventional welding techniques, a deep and sufficient penetration to the groove face located on both sidewise portions of the welding line is not obtained with complete satisfaction when extremely thick plates are butt welded with a narrow gap I groove.
Accordingly, an arc welding technology has long been desired that enables to obtain sufficient penetration in case of welding of narrow gap I groove of thick plates.